C++ :

#include<cstdio>
using namespace std;
int main()
{
	int s,i,n;
	scanf("%d",&n);
	s=0;
	for(i=1;i<=n;i++)
	{
		if(i%2==1)
		{
			s=s+i;
		}
	}
	printf("%d\n",s);
	return 0; 
}

Pascal :

Program jjisgay;
 var
   n,i,v:longint;
 begin
   read(n);
   for i:=1 to n do
      if (i mod 2=1) then v:=v+i;
   write(v);
end.